Packed towers are used for mass transfer operations such as absorption, desorption, extraction, scrubbing and the like. The function of the packing is to facilitate mass transfer between two fluid streams, usually moving countercurrent to each other. Efficiency and rate of mass transfer are enhanced by providing large surface area in the packing to facilitate contact of the fluids and by breaking the liquid into very fine droplets to enhance mass transfer to a gas phase.
U.S. Pat. No. 4,724,593 describes an improved method for manufacturing high performance, symmetrical, open volumed packing bodies. The high performance packing bodies have performed well and have captured a significant share of the market. An open, non-obstructive structure provides low pressure drop while dispersing and distributing flow in both longitudinal and lateral directions.
While the void volume of the interior structure of the packing body is less than prior high efficiency packing bodies, the structure normal to the longitudinal axis is still difficult to provide and manufacture requires several bending and rolling operations to form the sheet material into a packing body.
An improved packing body is disclosed in U.S. Pat. No. 5,498,376 issued Mar. 12, 1996, the disclosure of which is expressly incorporated herein by reference. A perforated strip of material is simply rolled into a spiral or into a concentric cylinder structure. The improved packing bodies have a high degree of open space, from 30% to 98%. Surprisingly, the rolled packing bodies are found to provide better mass transfer and efficiency than prior packing body structures.
Packing bodies having substantially open structure with good baffling action formed by folding and bending adjacent perforated panels along fold lines to form packing bodies in which the plates are substantially parallel to each other are disclosed in U.S. Pat. No. 5,458,817 issued Oct. 17, 1995.
Packing bodies are produced with complex shapes in a simplified manner from separate, perforated plates which are stacked in parallel relation. They are fixed in that relation by spacing means such as projections from the surfaces of the segments or side members such as bent or separate perforated side plates adhered to the side edges of the stacked segments. The plates also include baffle means for increasing disruption of the fluid into droplets.
The projections from the surface of the segments can also be used as baffles to disrupt large droplets, to create local turbulence, to increase contact between gas and liquid and to facilitate mass transfer. The projections can be polygonal tabs raised from the surface. The baffle tabs can be diamond, rectangular or circular in shape. Thin cylindrical rod projections from the surface have been found to be very effective in facilitating mass transfer while providing an open volume of above 30% with very low pressure drop.
Highly efficient packing bodies have recently been developed which utilize some longer rod projections to space and/or latch adjacent plates together. All of the baffle elements are rod-like projections and are substantially parallel to each other. All of the rod-like elements are releasable from a mold. The panels can be manufactured from a single mold and latched together to form a stacked packing body. The preferred latching means are sockets provided in the bottom surface of the adjacent panel. The latching rods can be tapered and are frictionally engaged in an opposed socket. Adhesive can be used to assure that the panels do not separate.
The panels can be successively reduced in size to form packing bodies having complex, polygonal shapes approaching spherical by simply molding a plurality of panels of different shapes and sizes. The panels can be square, rectangular, circular or oval. A differently shaped body can also be provided by cutting a square body across several panels to form a facet shaped member.
These packing bodies have a high degree of open space provided by perforations, at least about 30% of the packing body is open space, preferably from 50% to 98% of the body is open space. The rods provide increased surface for fluid contact.
The plates can be formed of metal, thermosetting resins, thermoplastic resins or ceramic precursors such as metal oxides dispersed in organic binder resin. The perforated plates are formed by molding organic resin materials. After the plate is in its final configuration, the plate can be fired to cure the resin or convert the precursor to a final ceramic state.
These packing bodies can be produced from much simpler starting materials. Even if molds are used to form the plates, the molds are much cheaper and simpler than molds used to form prior high performance packing bodies. Packing bodies can be formed in complex shapes that can not be practically made by other techniques and can be produced at much lower costs.
The stacked packing bodies 10 as shown in FIG. 1 (Prior Art) tend to entangle due to open rods 12 projecting from the bottom plate 14 which can enter the openings in the top plate and become entangled with rods in the sides or bottom of an adjacent stacked packing body.